LOW-PRESSURE INDUCTIVELY-COUPLED PLASMA ION-SOURCE FOR MOLECULAR AND ATOMIC MASS-SPECTROMETRY

A low-pressure inductively coupled plasma system is described which ca n be used for both molecular and atomic mass spectrometry. Element-sel ective detection of organotin, organolead, organoiron, and organohalid e compounds was possible using this source coupled with gas chromatogr aphy. Detection limits were as follows: tetraethyllead, 13 pg; tetrabu tyltin, 35 pg; ferrocene, 33 pg; iodobenzene, 25 pg; bromobenzene, 50 pg; and chlorobenzene, 500 pg. By decreasing the power and plasma gas flow it was possible to sustain a helium plasma using only the carrier gas from the gas chromatograph, and mass spectra were obtained for ch lorobenzene, bromobenzene, and iodobenzene that were similar to those obtainable using an electron impact ionization source. The molecular i on for chlorobenzene was observed to 10 ng injected on-column. The eff ect of power on the mass spectrum was investigated. By adjusting the p lasma gas flow and forward power, it was possible to influence the deg ree of fragmentation of the organic species. The potential exists for the development of a variable ion source with the ability to adjust th e degree of fragmentation simply and rapidly.